1. Field of the Invention
The present invention relates generally to catheters, and more particularly, to an ablation catheter for use in heart surgery, the catheter having an axially displaceable electrode to allow the formation of long endocardial lesions in the cardiac chambers of the heart.
2. Description of the Prior Art
A representative prior art ablation catheter having a movable electrode is disclosed in PCT/GB97/01270 to Morgan et al., the rights to which are assigned to the assignee of the present invention. The Morgan application discloses a catheter having a sliding ring electrode telescopically disposed over the catheter shaft and a remote mounted actuator for moving the sliding electrode. A sheathed conductor is disposed in a longitudinal channel formed in the catheter. The conductor is connected at one end to a controllable source of RF energy and at a second end to the conductor. The sheath provides electrical insulation for the conductor as the conductor is moved axially along the probe shaft. The actuator mechanism is configured to push or pull the electrode towards and away from the distal end of the probe by advancing or withdrawing the sheathed conductor along the catheter shaft. In this manner, contiguous endocardial lesions may be created in the cardiac chambers by applying radio frequency current to the sliding electrode. This expedient requires, however, that the conductor/actuator wire have sufficient column strength to resist buckling under load.
It is an object of the present invention to provide an ablation catheter having a sliding electrode for creating endocardial lesions.
It is a further object of the invention to provide an ablation catheter having a sliding electrode in which xe2x80x9cpullxe2x80x9d wires or cables are employed for improved actuation with better reliability.
It is yet another object of the invention to provide an ablation catheter having a sliding electrode which reduces the likelihood of actuation wire kinking or damage.
It is yet another object of the invention to provide an ablation catheter having a movable electrode which can be displaced in successive, predetermined increments to create continuous endocardial lesions.
In accordance with the above objects and additional objects that will become apparent hereinafter, the present invention provides an ablation catheter comprising, in an exemplary embodiment, a probe having a proximal end and a distal end and an electrode which is axially displaceable along the probe. A first pull cable is attached to the electrode, extends from the electrode towards the distal end of the probe, and doubles back through the catheter for pulling the electrode toward the distal end of the probe. The first pull cable is disposed within a lumen formed in the catheter that extends substantially from the distal end to the proximal end. A second pull cable is attached to the opposite end of the electrode and extends from the electrode toward the proximal end of the catheter for pulling the electrode away from the distal end. The second pull cable is disposed within a lumen formed in the catheter. Both pull cables are coupled to an actuator mechanism at the proximal end of the catheter for effecting axial movement of the electrode relative to the distal tip of the probe by selectively tensioning the respective pull cables. A second electrode may be provided at the distal end of the catheter. In that arrangement, the first pull cable exits the catheter through an opening in the fixed electrode.